Vinyl aromatic polymers stabilized with nu-methylaminoalkanols



United States Patent AROMATIC POLYMERS STABILIZED WITH N-METHYLAMINOALKANOLS William K. Schweitzer, In, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich, a corporation of Delaware No Drawing. Filed July 2, 1956, Ser. No. 595,068

6 Claims. (Cl. 26045.9)

VINYL in which it is exposed, the temperature and the presence or absence of sunlight. Such changes result in lowering of Y the mechanical properties of the polystyrene and impairment of its appearance. This characteristic is shared to more or less extent by other vinyl aromatic polymers containing 70 percent by weight or more of one or more monovinyl aromatic hydrocarbons of the benzene series in the polymer molecule such as polystyrene, polyvinyltoluene, copolymers of at least 70 percent by weight of styrene and not more than percent of a copolymerizable monoethylenically unsaturated organic compound, e.g. alpha-methyl styrene, acrylonitrile or methyl methacrylate. Since the uses of such polymers include the manufacture of molded articles, films, sheets, rods, bars, tubes, etc., either embrittlement or discoloration of the polymer is to be avoided. The provision of stabilized compositions consisting essentially of one or more vinyl aromatic polymers is the principal object of the invention.

According to the invention the foregoing object is attained by intimately incorporating with a thermoplastic vinyl aromatic polymer containing at least 70 percent by weight of one or more monovinyl aromatic hydrocarbons of the benzene series in the polymer molecule, from 0.1 to 5 percent by weight of a tertiary amine selected from the group consistingof the monoand dimethyl N-substituted alkanolamines containing from 2 to 5 carbon atoms in an alkanol group and 3-dimethylamino-1,2-propanediol. Articles made from the resulting compositions show little, or no, tendency to discolor upon prolonged exposure to light, e.g. sunlight, or light rich in ultraviolet rays, and exhibit little tendency to become brittle as a result of such exposure.

The tertiary monoand dimethyl N-substituted alkanolamines containing from 2 to 5 carbon atoms in an alkanol group and dimethylamino-l,2-propanediol have been found to be far more efiective agents for inhibiting the discoloring and embrittling efiects of light on vinyl aromatic polymers than are closely related tertiary amines 2,938,882 Patented May 31, 1960 such as diethylaminoethanol or diethylamino-1,2-propanediol, containing higher alkyl radicals as substituents on the nitrogen atom. v

The tertiary monoand dimethyl N-substituted alkanolamine stabilizers can be incorporated with the vinyl aromatic polymer in usual ways such as by heat-plastifying the polymer on compounding rolls, in a Banbury mixer or a plastics extruder and intimately blending the stabilizing agent therewith or by dissolving the polymer and the stabilizing agent in a common solvent and evaporating the latter to recover the polymer having said agent dispersed throughout.

In practice the vinyl aromatic polymer is usually heatplastified on compounding rolls, in a Banbury mixer or a plastics extruder and the stabilizing agent intimately blended therewith to obtain a uniform composition, which is cooled and cut or ground to a granular form suitable for molding.

Small amounts of additives such as dyes, colors, pigments, plasticizers, lubricants, mold release agents, etc., can also be incorporated with the compositions, but such additives are not required. When used, the additives are usually employed in amounts of from 0.1 to 10 percent by weight of the polymer.

The following examples illustrate ways in which the principle of the invention has been applied, but are not to be construed as limiting its scope.

EXAMPLE 1 Granular molding grade polystyrene was blended with 0.5 percent of its weight of l-dimethylaminoethanol by tumbling the ingredients in a laboratory blender. The mixture was fed to a laboratory extruder wherein it was heat-plastified and subjected to mechanical working, there'- by intimately incorporating the ingredients with one another, then was extruded, cooled and cut to a ganular form. Portions of the composition were injection molded to form test pieces having the dimensions 2 x 2 /2 inches by 0.1 inch thick. These test pieces were used to determine the efiect of the added agent for inhibiting the discoloration of the polystyrene upon exposure to out-ofdoors weathering. The procedure for determining the stabilizing action of the added agent was to measure the percent of light of wave lengths between 420 millimicrons and 620 millimicrons transmitted through a molded test piece when first prepared. The difiference between the amount of light transmitted at wave lengths of 420 millimicrons and that transmitted at wave lengths of 620 millimicrons represents a measure of the color of the composition. The test pieces were exposed to out-ofdoors weathering in the State of Florida U.S.A. at about latitude 25 North on a rack facing South with the test pieces inclined at an angle of 45 degrees above horizontal for a period of six months. test pieces to out-of-doors weathering for the prescribed time, the test pieces were removed and again tested for their color or ability to transmit light of wave lengths between 420 and 620 millimicrons. The difierence between the amount of light of said wave lengths transmitted through the test piece represents a measure of the color of the test piece after said exposure. The difierence between the color of a test piece of the composition to the out-of-doors weathering after exposure and the color of After exposure of the,

tested for color employing procedures similar to those employed in Example 1. For purpose of comparison, test pieces of the polystyrene alone were prepared and tested under similar conditions. The results are reported in Table III. h

the test piece as initially prepared is a measure of the Table III color change or degree of discoloration of thepolymer upon exposure to weathering. The darker the polymer Stabilizing Agent the greater is the difierence. For purpose of comparison, Initial Final Color test pieces of the polystyrene alone were prepared and Kind Percent change tested under similar conditions. The results of the experiments are reported in Table 1. None M 71.8 227 mg 3-dimethylamlno-1,2-propanediolh- 0. 5 5. 6 7. 4 1. 6 Do 1.0 5.7 0.1 0.4 Table I 1.5 5.8 5.5 0.3 2.0 5.1 5.6 0.5 Stabilizer Per; lniltial Fii1da1 1(llolor 11 can Ct? 0O 01 C 8 go 4 i ii'ei'heh'inhheihhhiiii 31-2 3.1% ii? 211 "F Series 9 exPerimentsifine r e by i i 5 Weight of 3-d1methylam1no-L2-propanedrol was mtimately incorporated with a resinous vinyl aromatic .polymer EXAMPLE 2 as identified in the following table, employing procedure 7 similar to that employed in Example 1. Portions of the In each a sane? 9 e xpenmentsvgranular P g m e0 composition were injection molded to form test pieces grad; eg e g e i r i g ae qg having the ihheheieih 2 ii 2 /2 inches by 0.1 inch thick. riate i an 2 m amme m amolm an n w These test pieces were tested for color, were exposed to tlfied m the following table employmg progedure slmllar out-o-doors weatherin and a ain tested or color emto that employed in Example 1. Portions-10f the com- 1 i dur t m I E 1 position were injection molded to form test pieces having H p 9 g proce es 8 at 056 e oye m r i e the dimension 2 x 2 /2 inchesby 0.1 inch thick. f The F Purpose of FP i the'vmyl test pieces were exposed to out-of-doors weathering in the i wlthout the V F P Q' State of Florida U.S.A. for ii period of 3 months. Table r w were l and te e under slfflllar 001M11- Il identifies the experiments, names the alkanolamine Table f Vinyl afomatlc P M and gives the amount employed based on the weight of the O P Y gives the 11111131 9 c0101" after polystyrene. The table also gives the initial color of the 3 weathering and the color change determined for the polytest piece, the color after exposure to weathering andthe mers.

Table II Alkanolamlne 5 Run No. 5 i Final Color color color change Kind Percent (Hio)iNoHioHioH 0;.5 4.1 7.3 5.2 HSOMNGHiOHiGHiOHHHh 0.5 3.5 8.0 4.5 (-HsC)2NCH2CHzCH2GHzOH-; '0. 5 3:5 7. 6 4. 1 (H)ZNCHZOHQCHZCHZOHQOH- 0.5 4. 0 7. 6 a. 0 (HQOMNGHQCHOHOH i 05 a7 7.4 3.1 H3CN(OH2OH2OH)2. t 0.5 5. 3 7. 6 23 None .h 0. 0 e1. 8 22. 7 20. 9

color change. Forpurpose of comparison test pieces Table IV of the polystyrene Without a stabilizing agent were pre- 5 pared and tested under similar conditions; The results i 3-Djm'ethy1- 1' obtained werg as follows; i i R1111 Polymer Kind aminolnltial Final Color No. 1,2-procolor color change panediol, EXAMPLE 3 Percent In each of a series of experiments, 'granular'polystyrene Polyistyrenen; I having a nolecular weight corresponding to a viscosity 116 2913 5 characteristic of 22 centipoises as determined for a '10 percent by i of weight percent solution of the polystyrene 'in toluene at 6.3 23 2 5 was blended With 3-dlme'thy1amln0-L2-p1t0pane: Polyvinyltoluene, 0.0. 2.0 26.4 23.5 diol in amount as stated in the following table lay-tumbling ig g ffifigyg' aflTgi' l i 8 i1; i313 1313 m a laboratory blender. The mixture was fed to a V rene25% e laboratory extruder wherein it was heat-plastified and L0 3.8 4.9 i mechanically Worked at a temperature of about 400 F. 9 Copolymerof 70% 'sty- 0- -8 3 -7 for a period of about 0.5 minute, then was extruded, 5535 aerylom' cooled and cut to a granular form. V Portion of h 10 di to 11.4 11.1 0.3 position were injection molded to form test pieces havmg the dimensions 2 x 2% inches by 0.1 inch thick. i i The molded pieces were tested for color, then exposed I claim: p 7 i to weathering for a period of three months and again l. A' composition of matter the essential constituents of which are a vinyl aromatic polymer consisting of at least 70 percent by weight of a monovinyl aromatic hydrocarbon of the benzene series having the vinyl radical directly attached to 'a carbon atom of the benzene nucleus, and not more than '30 percent by weight of a monoethylenically unsaturated organic compound selected from the group consisting of alpha-methyl styrene, acrylonitrile and methyl methacrylate, chemically combined in the polymer molecule and as a stabilizing agent therefor, from 0.1 to 5 percent, based on the Weight of the polymer of a tertiary amine selected from the group consisting of 3-dimethylamino-l,2-propanediol and the monoand dimethyl N-substituted alkanolamines containing from 2 to 5 carbon atoms in the alkanol radical and a single nitrogen atom in the molecule.

2. A composition as claimed in claim 1, wherein the stabilizing agent is 3-dimethylamino-1,Z-propanediol.

3. A composition as claimed in claim 1, wherein the stabilizing agent is dimethylaminoethanol.

4. A composition as claimed in claim 1, wherein the stabilizing agent is methyldiethanolamine.

5. A composition as claimed in claim 1, wherein the stabilizing agent is l-dimethylamino-Z-propanol.

6. A composition of matter, the essential constituents of which are polystyrene and as a stabilizing agent therefor, from 0.1 to 5 percent, based on the weight of the polystyrene, of 3-dimethylamino-l,2-propanediol.

References Cited in the file of this patent UNITED STATES PATENTS 2,287,188 Matheson et a1. June 23, 1942 2,681,328 Stanton et al. June 15, 1954 2,732,366 Tubbs et a1 Jan. 24, 1956 2,809,955 Matheson et a1. Oct. 15, 1957 2,810,707 Nagle et a1. Oct. 22, 1957 FOREIGN PATENTS 662,314 Great Britain Dec. 5, 1951 

1. A COMPOSITION OF MATTER THE ESSENTIAL CONSTITUENTS OF WHICH ARE A VINYL AROMATIC POLYMER CONSISTING OF AT LEAST 70 PERCENT BY WEIGHT OF A MONOVINYL AROMATIC HY DROCARBON OF THE BENZENE SERIES HAVING THE VINYL RADICAL DIRECTLY ATTACHED TO A CARBON ATOM OF THE BENZENE NUCLEUS, AND NOT MORE THAN 30 PERCENT BY WEIGHT OF A MONOETHYLENICALLY UNSATURATED ORGANIC COMPOUND SELECTED FROM THE GROUP CONSISTING OF ALPHA-METHYL STYRENE, ACRYLONITRILE AND METHYL METHACRYLATE, CHEMICALLY COMBINED IN THE POLYMER MOLECULE AND AS A STABILIZING AGENT THEREFOR, FROM 0.1 TO 5 PERCENT BASED ON THE WEIGHT OF THE POLYMER OF A TERTIARY AMINE SELECTED FROM THE GROUP CONSISTING OF 3-DIMETHYLAMINO-1,2-PROPANEDIOL AND THE MONO-AND DIMETHYL N-SUBSTITUTED ALKANOLAMINES CONTAINING FROM 2 TO 5 CARBON ATOMS IN THE ALKANOL RADICAL AND A SINGLE NITROGEN ATOM IN THE MOLECULE. 